There are a number of different devices which are used for rapid, accurate spectral analysis of the reflectivity, transflectance and/or transmitivity of a sample. One of these devices, disclosed in U.S. Pat. No 4,540,282 to Landa et al. (the Landa patent), is a device which enables immediate and rapid analysis of a number of different products. This type of device measures three generalized characteristics: the chemical constituents of the sample, the physical constituents of the sample, and the quality parameters of the sample.
The chemical constituents of a product include such things as the octane number in gasoline or the amount of aromatics in gasoline. In another environment, such parameters as the amount of protein, starch, or oil of food may be measured. In yet another environment, such blood constituents as glucose or cholesterol can be measured using such a device. In the area of pharmaceuticals, the drug composition a sample can be determined and such features as the active zones of drugs can be measured. In the tobacco industry, such chemical characteristics as nicotine, tar and menthol can be measured using such a device.
The second broad type of characteristics which can be measured using such a device are called physical parameters. Such physical parameters include characteristics such as the viscosity of liquids. In addition, such characteristics as molecular weight of a sample may be measured.
The third area which can be measured using the device as described in the Landa patent are quality parameters. Such quality parameters which may be measured by the device described in the Landa patent include such things as the taste of beers or wines. Since beer and wine each have a unique spectral signature, it may be possible to determine the quality of wine by comparing the spectral signature of a wine to be analyzed with a known product or standard. For example, once the quality of a particular wine is known, it may be possible to take a spectral signature of that wine and determine which spectral characteristics or signature wine must have in order to have a similarly good taste. Thereafter, wines need not be taste-tested in order to determine their quality. A spectral analysis only need be done and the signature be analyzed in order to determine quality.
As stated above, the device described by the Landa patent is capable of determining the spectral characteristics of a number of different products in a number of different forms.
There are basically three modes of introducing and detecting light from a sample. The first way is through reflectance. In the reflectance mode, light is introduced onto a sample. The light which is reflected is then relayed back to a detection apparatus such as the device taught by the Landa patent.
The second mode of operation is transmittance. In this mode, light is passed through a sample and the light passing through the sample is received and transmitted back to the apparatus for analyzing the light.
The third mode of operation is the transflectance mode. In this mode, light is passed through a sample. Part of the light is reflected and transmitted back to the apparatus for optically analyzing the light. The portion of the light which is not reflected passes through the sample to a mirror or other reflecting surface. The light is then passed back to the sample and again transmitted to the apparatus for analyzing the light.
In order to obtain the best results, it is necessary that the sample be in a state which allows easy and accurate access. For example, it may not always be possible to insert a light probe or the light within a stream of flowing liquid. Therefore, a part of the liquid must be tapped and run through a flow-through cell. The flowthrough cell must pass the liquid through the light stream with the stream being laminar or turbulent flow.
It is therefore an object of the invention to provide a flowthough cell which enables a sample to be readily detectable.
It is yet another object of the invention to provide a flowthrough cell with a variable optical path.
It is yet a further object of the invention to provide a flowthrough cell which is modular.
It is yet a further object of the invention to provide a flowthrough cell which enables easy access to component parts in the event that a component part is defective.
It is yet a further object of the invention to provide a compact flow-through cell.
It is yet a further object of the invention to provide a flowthrough cell which enables flow at high pressures.
It is yet a further object of the invention to provide a flowthrough cell which includes a device for heating the fluid passing therethrough.
These and other objects are achieved by the present invention.